Image forming apparatus and image density control method

Abstract

An image forming apparatus is disclosed that includes an image density control unit that performs control operations based on an image density control condition that is adjustably set to control an output image to have a predetermined image density, an image density control condition modifying unit that calculates a modified image density control condition based on information on an amount of toner exchanged at a developing apparatus within a predetermined period and a parameter for image density control condition calculation and sets the modified image density control condition as the image density control condition to be used by the image density control unit, and a parameter modifying unit that modifies the parameter for image density control condition calculation used by the image density control condition modifying unit based on a toner pattern detection result obtained by detecting a toner pattern formed on a belt member.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an image forming apparatus such as a copier, a printer, or a facsimile machine that forms an image using a two component developer made up of toner and a magnetic carrier, and an image density control method.[0003]2. Description of the Related Art[0004]The two component development system is a conventionally known technique that involves supporting a two component developer made of toner and a magnetic carrier (simply referred to as ‘developer’ hereinafter) on a developer carrier, forming a magnetic brush with the magnetic developer by the magnetic pole provided within the developer carrier, and developing a latent image on a latent image carrier with the magnetic brush. The two component development system is widely used since it enables color imaging with relative ease.[0005]It is noted that in forming an image, an image forming apparatus has to maintain a constant image density. The i...

AI Technical Summary

Benefits of technology

The present invention provides an image forming apparatus and an image density control method that can reduce the consumption amount of toner used for operations other than image formation while maintaining a fixed image density by adequately responding to changes in the developing capacity of a developing apparatus caused by environmental change. This is achieved by modifying the image density control condition based on information for determining an amount of toner exchanged at the developing apparatus within a predetermined period and a parameter used for image density control condition calculation, and controlling the image density of an output image based on the modified image density control condition.

Problems solved by technology

However, it is relatively difficult to control the amount of charge of the toner used in the image development to a predetermined target value for obtaining a desired image density.

As a consequence, stable developing capacity may not be achieved even if the developing potential and the toner density may be maintained constant and in turn, a desired image density may not be obtained.

In this case, toner is likely to reside within the developing apparatus for a relatively long time.

Toner residing within the developing apparatus for a relatively long time may be stirred for a long time so that a large portion of the toner used in image development may have a charge that is greater than the desired charge.

On the other hand, in the case of outputting an image with a high image area ratio, a large portion of the toner residing within the developing apparatus may be new toner that has just been supplied and is not yet adequately charged so that a large portion of the toner used in image development may not be charged to the desired charge level.

In turn, there is a growing number of instances in which toner used for image development is not adequately charged to the desired charge level during image formation performed after outputting an image with a high image area ratio.

That is, the developing capacity cannot be maintained constant even when the developing potential and the toner density are maintained constant so that a fixed image density cannot be achieved.

However, the image forming apparatus according to Japanese Laid-Open Patent Publication No. 2007-133235 does not have measures for responding to factors other than the amount of toner exchanged at the developing apparatus within a predetermined period of time.

For example, the above-described apparatus is not configured to respond to fluctuations in the developing capacity of the developing apparatus due to environmental change or variations in standby time so that image density may still not be adequately controlled.

For example, similar problems may occur in a case where the control reference values for toner density and developing bias as image density control conditions are fixed while a control reference value for the writing light as another image density control condition is corrected based on the toner exchange amount information.

Also, similar problems may occur in a case where the control reference values for toner density and writing light as image density control conditions are fixed while a control reference value for the developing bias as another image density control condition is corrected based on the toner exchange amount information.

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